Internal combustion engine



July 2, 1935. E;' DASSET INTERNAL COMBUSTION ENGINE Filed March 19, 1954 2 Sheets-Sheet 1 [rive/M01;

5177i Ze 17/7551 M 2, 1935. E DASSET 2,006,498

INTERNAL COMBUSTION ENGINE Filed March 19, 1934 2 Sheets-Sheet 2 17 119 27955.57 f fll'forngy.

Patented July 2, 1935 umrsn STATES PATENT OFFICE Application March 19, 1934, Serial No. 216;.385 In Belgium January 15,1934

3 Claims. (Cl. M 55) This invention relates to improvements ininternal combustion engines and explosion motors.

The transformation of rotary into reciprocating motion by means of cams, namely the transmission of motion from a revolving shaft to reciprocating pistons by means of cams secured on said shaft and in engagement with rollers carried I by saidpistons, is well known, and has found use for instance in pumps and in compressors.

explosion motors, according to which the pistons generally diametrically opposed with relation to the shaft, operate by means of rollers mounted at the ends of the piston rods, and bearing on cams secured on the shaft. These engines or motors have not found practical application.

Generally in engines of this type with diametri cally opposed cylinders, diametrically opposed pistons are connected in pairs and the two piston rods each carry a roller which rolls on the periph cry of a cam secured on the shaft. To avoid the T use of double cams, one has proposed a single cam rollers with their common cam;-this condition restricted the profile chosen forthecam and required cams of large dimensions which increased the bulk of the engine and did not permit of transforming crank-shaft into cam-shaft engines without changing the whole casing. Neither was it possible to obtain at the start a powerful motor torque.

erally is a portion of a circle. Also in the design 'of these profiles, the motive torque, principally at the start, or the heating of the engine, or the loss of power in theperiods during which thecam is. motive with relation to the rollers, are not taken 1 into consideration, and none of the solutions proposed up to this day have been found applicable.

The present invention is the result of long and numerous experiments onnewly constructed env in space is limitedby the existing casing.

results, particularly with old. engines which hav- In' theory the reverse transformation by the same- All the cams proposed up to this day and designed for a four-stroke engine have a regular profile, the three-quarters of'which gening been'transformed and simplified by the pres-.

ent invention have run for thousands ofmiles, with greater'efiiciencythan when they were new, noticeably with complete absence of vibrations.

The invention is designed to be applied more particularly to engines with cylinders in. a row, each piston acting "upon a, separate cam; the invention can however beapplied to engines with radially disposed cylinders, .but each piston must work independently. ;;The invention is characterized essentially by the fact. that-the, motive roller of each: piston, that is the roller which thrusts against thecorresponding cam duringthe expansion stroke of the piston, is shifted laterally in relation to the straight line which is parallel. to the axis of the cylinder and intersects the axis of the shaft.

In otherwords, if one considers a piston movable along a verticalline, the shaft being hori zontal,the-motiveroller is outside thevertical line passing through the axis of rotation. Thisv can be constructed, ,either'by keeping the axis of the piston in; the vertical line passing through the axis ofthe; shaft and laterally displacing with relation to thatlinethe axis of the motive roller,

or by mounting the axis of the roller in the axis line of the piston which is then displaced laterally to the vertical line-passing through-the axis of rotation of the ,cam; Preferablythe motive rollerfis combined with a guide roller carried by a rigid element supporting the motive roller, and

. disposed insuch: a manner that the cam is located between the" two rollers; the said guide roller can be displaced laterally like the motive roller, but in opposite direction. When a single sided carnsurface is usedithe' second guide roller is necessary, unless there.. are'two, oppositely disposed cylinders, inwhich case the motive roller of each pistonis a guide roller for the other. piston. The guide-roller fulfills several functions: In the first place it produces the admission stroke of the-"piston, secondly it limits the, exhaust stroke'of the piston and prevents same from knocking against the piston-head by force of inertia. Contrarily to what has been hitherto proposed it is not necessary to maintain both rollers in permanent'contactwith the cam; contact is sufiicient at the ends of the piston strokes and this allows to obtain profiles for the cam which are much'mo're interesting than those obtained up till now, particularly when it is re-, quired to transform a crank-shaft motor whereprofile of the cam, a motor torque much more powerful at the start; it also allows to establish cam profiles which at the start of the downward stroke of the piston (expansion) produce a rapid displacement of the piston, thereby a quick expansion stroke and gives greater mechanical efficiency with less heat. Motors according to this invention have worked for several hours at full power without artificial cooling and have remained comparatively cool.

The lateral displacement or shift of the motive roller enables to obtain an infinite number of profiles for the cam giving high mechanical efficiency; it also enables, for a determined length of the stroke, considerably to reduce the space required for the cams, and to avoid undesirable reactions principally when the cam acts uponthe rollers for the exhaust, admission and compression strokes. v

Concerning the reactions and loss of power due to the action of the cam upon the rollers,..an.

important feature of this invention is that the profile of the cam, in the portion thereof which engages the roller or rollers to force displacement of the piston, is established in such a: manner that at each instant the point of contact j between the cam and'the respective roller is on the line described by the centre of the respective roller, or at the utmost on the straight line which joins the centre of the respective roller to the.

centre of the shaft. ,1

Contrarily to what has been done up till now,

the design of the profile of the cam is devised,-

besides with the above mentioned conditions, with consideration of the available space for the casing, the length of piston stroke, and the diameter- Cams according to this inventionof the shaft. as well as the manner of'obtaining same, and the disposition of the rollers have been illustrated by way of example in the appended drawings wherein:

Fig. l-is a schematical view in section of an engine of the type considered in this specification,-

Figs. 2 to 6 are profiles of' cams with the rollers, and showthe manner of obtaining'same In each case the same stroke of the piston willbe considered, also a lateral displacement of each roller equal to the radius of the rollers, the two rollers having the same radius. Also the vertical lines passing through the axis ofrotation of the cam and the axis of the motive rollerare distant by a length equal to the radius of the shaft. It will be assumed that each roller has a diameter qual to the diameter of the-shaft, and that both rollers move vertically.

Fig, 1 schematically illustratesthe mountingof a cylinder and piston in relation to the corresponding cam. 3|] is the casing of the engine, inside which is mounted the power shaft 3|. The cylinders 32 are mounted in a line above the casing; the piston 33 has pivotally connected thereto the piston rod 34 which extends right into the casing 30 and is provided with a slotted portion through which extends the shaft 3 I. slot 35 has an inner width equal to the diameterof the shaft and a length equal to the stroke of the piston. Preferably the extended portion of the piston rod comprises two' identical and par allel slotted portions disposed 'on either. side of.

the cam 35 secured on the shaft 3| and rigidly rolling on the periphery of the cam 36 the profile of the cam and the exact position of the rollers are determined hereafter.

With reference to Fig. 2, from a point taken as centre, a circle 3 having a radius equal for instance to V of the piston-stroke is described. The vertical diameter is drawn, and on either side of this vertical diameter, at a distance equal to the diameter of the power shaft, the two vertical lines I, 2 are drawn. On the left-hand side line I, a centre 4 outside circle 3 is chosen in such a manner that a circle 5 described from such a centre, with the radius of the motive roller, is tangent to circle 3. This circle 5 shows the motive roller in the position it will occupy at the instant of the explosion, or a moment after. The point 6 which is at the intersection of circle 3 and the vertical diameter being chosen as the apex of the cam, the centre of rotation O of the cam is determined by taking on the vertical diameter, below point 0, a distance equal to half the radius of circle 3, minus 1 5 of the stroke of the piston, that is of the stroke.

If one consider the portion of the circle 3 comprised between the point 6 and the point I as being a portion of the profile of the cam, it will be seen that in the position illustrated for the motive than the moment of 10 about 0'. The two torques being in opposite senses, the cam will rotate according to 11 clockwise, and the operation of the cam by the roller may be compared to a reaction.

- The same operation will-take place for the whole portion of the circle comprised between 6 and T on the left, with a resultant torque decreasing from 6 to I, and for all the points comprised within said portion of circle, with an increased resultant torque, that is;to say for the profiles of cam comprised within the portion 6-1 of the circle, and

in which the distance to the centre 0 decreases from 0'6 to 0'1. The power receiving portion of the cam, that is the portion of the cam engaged by the motive roller during the expansion will be a curve with a continuously decreasing radius in relation to point 0, and which is comprised between the half circle 6I, and a straight line 6-8 end-,

ing in a portion of a circle around axis 0.

.The position of the centre of the lower roller 9 isdetermined as follows: from a centre taken on line I there is described a portion II! of a circle cor- I i responding to the lower position of the roller 5;

from O as centre there is described a circle having a radius equal to the distance between 0 and the point where the line I intersects the circle ID. On the vertical line 2 there is obtained point I I which is the point of tangency of the lower roller with the cam.

As aforesaid, the non-motive portion of the cam must be such that on all those points the contact with the motive roller and with the lower roller is on the lines I and'2 respectively. In order to determine this curve, from O a centre with a radius 0'6 a circle I2 is described; radius 0 I I intersects V r l2 connected at both ends. At' both ends and outthe clrcle at pomt a and am 6 '3 b dmded equally, for instance in eight equal portions. Radii are drawn through the points of division. On one of the lines I or 2, eight centres are marked, corresponding .to the positions of the centre of the 2;o0e,'49e

the radius of the motive shaft; The centre of upperfroller" after each successive eighth of the stroke; the circles," or 7 portions ofcircles repre senting the roller in the successive positions are I drawn as illustrated, and with 0" taken ascent're,

illustrated as being formed ofan arc of circle 6, 2 I, and of a curve '2 Itraced empirically but with" a radius decreasing from 2| to H. With a motivecurve of this type-there is'no permanentcontact of bothrollers with the cam; the simul taneous' contact of both rollers only takes-place at the end-of the stroke which is suflicient-as the lower roller'acts only to prevent the piston from striking'the head-of the cylinder at theend of the exhaust stroke. 7 When the cam operates the admission stroke, the upper rollercan remain outjof contact with the cam;

If desired, to ELVOld both the rollers with the cam may be provided; the

motive portion of the cam is'determined according to this invention by extending the radii which have given the'points "II and.- II to". On the vertical line] are drawn thearcs of circles corresponding to the different portions of the roller at each successive eighthof thestroke, and onejoins point O with the various points occupied" by the centre of the roller-"on the-vertical line I. These lines intersectthe respective circles at points 23, 24,25 etc. From 0 as a-c'entr'e 23 is transferred to 21-, 24 to 28 and so on, which provides the dotted line curve shown in Fig. 2, not very different from the full line curve.

The tracingofcurvefil I of the cam has been determined whilst assuming a constant speed of the piston when thecam operates one of the ?-rollers. In the same manner one could deter mine a profile; B- -H corresponding to" the es-- sentialcondit'ion given above for the forces, but which would also ensure a variable 'speed of the piston during the'whole strokeor during a por'- tion thereof, by action onthe lower roller (ad mission) as well'as on the upper roller (exhaust andc'ompression). The same thing could-be done for the'motive portion of the cam, for instance to allow right at thebeginning of the if explosion stroke a: high'speed of the piston, which tends to increase'the mechanical efficiency of the engine and-to'decrease the heating of same.

Fig. 3 shows an example of a cam profile determined as the full line portion of Fig. 2, but with this difference that the radius of the primitive circle 3 is equal, not to 7/8ths of the stroke but to the whole stroke. In this case portion 6-! of the cam coincides exactly with the left hand half portion of circle 3, Whereas the nonmotive portion of the cam, determined as in Fig. 2 by the points l4! 5 and under the same conditions intersects the circle 3. Such a profile of cam ensures an absolutely constant speed of the piston during the expansion.

In Fig. 4 a modification has been illustrated, according to which the rollers have been disposed the other way round in relation to the axis of rotation of the cam, with a different lateral displacement for each roller. From the centre 0, with a radius equal to the 7/8ths of the stroke, a circle 3 is described. On the right hand side of this centre and at a distance equal to half the radius of the motive shaft, the vertical line I is drawn,whereas thevertical line 2 is drawn on the left hand side at a distance equal to 3/2 of else, a permanentcontact of the 'shaft is determined as in Fig. :2 Ion the 'vertical line at equal-distance from lines I and 2. The vJcentre of the bottom roller for-the higher position'thereof is determined as in'Fig. 2,which gives the position '9 in dotted lines.

speed during the-expansion, the right hand portion 6, I l .of the curve" isdetermined in the same wayas before,-by dividingthe arc 'B.-|3 into eight equal portions'to obtain .points 40, 4!; 42". etc. Itwill be seen that the position of.

Fora downward movement:. of the piston atconstant the bottom roller; corresponding to "the upper position of roller 5 is not 9, but Booflesponding to the: tangent pos1t1onin146,.'not in H1". The

point .I l constitutes the point of inflexionfor the connection with the left hand side of the cam which,"for' the major part, is the circle 3 except from H to 2|. It will be verified that the .sense of rotation'is opposite to the sense of rotation in.

Fig. 2 and that there isfa wider range for giving advance to the ignition. than in Figs. 2 and'3,v

in which the angle of advance can correspond to portion 6, B at theutmos't. In the example of Figs..2 and 3, if it be assumed that the explosion takes place at theinstant the mechan-.

ism is-in the position illustrated, it'can be seen that atthatinstant the piston has already commenced the downwardstroke, whereas in Fig. 4 ithas not yet arrivedat the end of the compression stroke. 1 x

:In Figs- 2 and 3, as well .asin Figs. 5 and 6, the engine always runs with late ignition, whilst always giving a'direct'torque at the instant the.

explosion occurs. This arrangementis specially favourable becauseit completely avoids the vibrations due, in engines of the usual type which have'to work with. advance at the ignition, to the reaction betwen the vis viva oi the piston at the end of the compression stroke and the force .of explosion directed against the former.

Fig. 5'shows, a modification of Fig. 4, accordtions'of being tangent whereas-the other por tiorr is-y'practically identical to the corresponding portion" in Fig. 4. The position of the bottom roller which corresponds to the upper position of roller 5 is again angularly displaced with relation to the extreme upper portion 9 of the lower roller.

Fig. 6 gives an example of a cam devised for producing a powerful engine torque at the beginning of the stroke or at the explosion, together with a rapid descent of the piston at the beginning of the expansion stroke. It will be obvious that these conditions'would be best fulfilled by the cam profile 6-8 in Fig. 2, but this profile has the inconvenience of producing knocks on account of the successive losses of contact between the rollers and the cam.

ing to which the centre 0 of circle 3 is on the right hand side of all the centres, of the rollers In Fig. 6 the motive portion of the cam has been determined in such a manner that for the first 72 of rotation of the shaft, the upper roller and consequently the piston describes half of the stroke, whereas the other half is performed by motive portion of the cam, a whole series of proe files answering to various conditions for the cooling of, the engine, or for the motive torquecombination a power shaft, a piston movable'in' 'a plane perpendicular to said shaft, a piston rod: terminating with a slotted portion, said power,

shaft being engaged through the slot and the slot having a length equal to the stroke of the piston plus the diameter of the power shaft and a width equal to the diameter of the powershaft, a cam secured on the power shaft, a roller freely rotatably mounted at each end of the slotted portion ofsaidpiston rod and rolling on the periphery of the said cam whereby said piston operates said power shaft, the two rollers of said piston rod being of equal diameter and at an equal distance on either side of the straight line which passes through the axis of rotation of the cam and'is' parallel to the direction of displacement of the piston, the point of contact between the cam and the roller which forces displacement of the piston by the action of the cam, in said forced displacement of the piston, being comprised'between/the line'described by the centre of the roller and the straight line joining the centre 0 said roller to the centre of the shaft.

2. Internal combustion engine comprising in combination a power shaft, a piston 'movable in' a plane perpendicular to said shaft, a piston rod terminating with a slotted portion, said power shaft being engaged through the slot and the slot having a length equal to the stroke of the piston plus the diameter of the power shaft and a width equal to the diameter of the power shaft,- a cam secured on the power shaft, a roller freely rotatably mounted at each end of said slotted portion of said piston rod and rolling on thepecircle and it will be seen that at the startthe torque is very powerful. Whilst remaining with in the limits indicated in Fig. 2 concerning the:

riphery of the said cam whereby said piston operates said power shaft, the two rollers of said piston rod being of equal diameter and at an equal distance on either side of the straight line which passes through the axis of rotation of the cam and isparallel to the direction of, displacement of the piston, the said cam being excentered with relation to the axis of the power shaft, and having a portion, corresponding to the explosion stroke of the piston, formed of a curve of con-- stantly decreasing radius in relation to the centre of the power shaft, from an apex corresponding to thebeginning of the explosion stroke, to a point of minimum radius corresponding to the end of the explosion stroke, said cam having another portion, whereby it operates the roller for the compression stroke of the piston, such that the point of contact with said roller is constantly on the straight'line described by the centre of said roller. 7

3. Internal combustion engine comprising in combination a power shaft, a piston movable in a plane perpendicular to said shaft, a piston rod terminating with .a slotted portion, said power shaft being engaged through the slot and the slot having a length equal to the stroke of the piston plus the diameterof the power shaft and a width equal to the diameter of the power shaft, a cam securedon the power shaft, a roller freely rotatably mounted at each end of the slotted portion of said piston rod and rolling on the periphery of the corresponding cam whereby said piston operates said power shaft, the two rollers of said piston rod being of equal diameter and. at an equal distance on either side of the straight line which passes through the axis of rotation of the cam and is parallel to the direction of displacement of the piston, the said cam for said piston having a portion upon which acts the motive roller of the piston to force rotation of the power shaft formedof a portion of a curve comprised between a circle excentered with relation to the axis of the power shaft and a straight line joining the portion-of large radius to the portion of smaller radius of the cam, and a portion which acts upon theother roller to operate compression stroke of the piston, such that the point of contact with the latter roller is comprised between the straight line described by the centre of said roller and the straight line joining the centre of said roller to the centre of the shaft.

, EMILE DASSE'I. 

